The present invention relates to a method for machining a rotation-symmetrical workpiece surface, especially of crankshafts, wherein the workpiece is rotated during machining and the workpiece surface is first roughed and then smoothed with a cutting blade. The present invention further relates to a tool for performing the aforedescribed method.
In the machining of crankshafts it is known from European patent 0 211 216 and German Offenlegungsschrift 35 23 274 to perform a roughing process of the crankshaft by radially plunge-cutting by turning with a formed cutter. Subsequent to this roughing process, the finishing process of the crankshaft is performed by turning broaching in which the crankshaft is rotated at a relatively high speed while the disk-shaped tool is rotated at a relatively low speed. For each individual width of a crankshaft pin, special cutters for the turning broaching of the finishing process must be employed since the cutting edges extend at an angle relative to the axis of rotation of the tool and furthermore must be embodied in a dished fashion. During broaching turning the cutting edges penetrate at a very great negative angle into the crankshaft resulting in very high normal forces. This results in an increased wear at the cutting edges of the cutting elements and in an increased bending of the crankshaft during the turning broaching process. As a consequence, during broaching turning processes a rattling tendency is observed which leads to a reduced accuracy of the cutting process. Furthermore, during the machining of steel in a turning broaching process long, curled cuttings are produced which inhibit a reliable flow of cuttings within the tool and the machine. Especially with automated machines the removal of these long, curled cuttings is difficult and expensive. These long, curled cuttings furthermore differ considerably with variations of the excess material to be removed.
It is therefore an object of the present invention to provide a method of the aforementioned kind and a tool of the aforementioned kind with which the workpiece surface can be machined during the smoothing operation such that with low cutting material costs and a reliable cuttings removal a high precision at the workpiece surface may be achieved and only small cutting forces are generated.